Method for manufacturing polychromatic light emitting diode device having wavelength conversion layer made of semicondcutor

ABSTRACT

A method for manufacturing a polychromatic light emitting diode device, comprising steps of providing an epitaxial substrate and forming a multiple semiconductor layer on the epitaxial substrate, wherein the multiple semiconductor layer comprises an n-type semiconductor layer, a p-type semiconductor layer and an active layer. The active layer emits light of a first wavelength. Thereafter a first wavelength conversion layer is formed on the multiple semiconductor layer. The first wavelength conversion layer is made of semiconductor and absorbs a portion of the light of a first wavelength and emits light of a second wavelength, wherein the second wavelength is longer than the first wavelength.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of patent application Ser.No. 12/577,350 filed on Oct. 12, 2009 and assigned to the same assigneeof the present application.

BACKGROUND

1. Technical Field

The present invention relates to a light emitting diode device andmanufacturing method thereof, and more particularly to a polychromaticlight emitting diode device and manufacturing method thereof.

2. Description of Related Art

Commercialized white light emitting diode devices, built using thepresent light emitting technology, produce white light by mixing of red,green and blue light, which are separately emitted from red, green andblue light emitting diodes. However, the method has a disadvantage ofpoor mixture quality. When white light emitting diode devices are usedin a backlight source of a liquid crystal display, a diffusion plate anda brightness enhancement film can be utilized to enhance uniformity ofmixing light. On the contrary, when the white light emitting devices areused for lighting, uniformly mixing light cannot be easily obtained.Moreover, the lifespan of red, green and blue light emitting diodes aredifferent, and if any one fails, the color of light would becomeobviously imbalanced and harsh to users' eyes.

The current mainstream method uses light emitting diodes with phosphoruspowders to mix white light. For example, blue light emitted from nitridebased semiconductor light emitting diodes can be mixed with yellow lightemitted from an excited yellow phosphorus powder to generate whitelight. However, the method has a disadvantage of the short lifespan of ayellow phosphorus powder, and especially, the yellow phosphorus powderis disposed so close to the light emitting diodes with high temperaturesuch that its light conversion efficiency decreases beyond expectations.Moreover, phosphorus powders have an issue of low light conversionefficiency. However, the using an inorganic phosphorus powder for itslonger lifespan would obtain light conversion efficiency that is lowerthan those of organic phosphorus powders. Therefore, various researcheshave been carried out to develop white light emitting diodes withoutusing phosphor powers or to develop polychromatic light emitting diodes.

A paper titled “Monolithic Polychromatic Light-Emitting Diodes Based onInGaN Microfacet Quantum Wells toward Tailor-Made Solid-State Lighting,”Applied Physics Express 1 (2008)011106, discloses a method that usessilicon oxide stripes as a mask and epitaxially grows microstructuredInGaN/GaN quantum wells on unmasked areas. Due to the alteration ofgrowth conditions and mask geometry can be changed to emit variouswavelengths, light of various wavelengths can be mixed to generate whitelight. A paper titled “Structural and Optical Properties of In-RichInAlGaN Heterostructures for White Light Emission,” Japanese Journal ofApplied Physics, Vol. 47, No. 6, 2008, p.p. 4413-4416, discloses amethod that trimethylaluminium flow rate and reactor pressure areadjusted to form three-dimensional island structures during a metalorganic chemical vapor deposition process on a InGaN layer. Due to lowsurface mobility of aluminum atoms separate to in-rich phase, a broademission from green to red wavelengths can be observed. Combining blueemission from InGaN layer with green to red emission from In-richInAlGaN alloy layer, white light emission has been obtained.

A paper titled “Phosphor-free white light-emitting diode with laterallydistributed multiple quantum wells,” APPLIED PHYSICS LETTER 92, 091110(2008), relates to a method that a portion of structure of blue InGaNmultiple quantum wells is etched away, and green InGaN multiple quantumwells are epitaxially grown on the etched portion. Thus, the finalstructure can emit blue and green light. Another method, which is usedto produce a multiple quantum well structure including different singlequantum well layers each emitting corresponding blue or green light, isdisclosed in a paper titled “Phosphor-Free GaN-Based Transverse JunctionLight Emitting Diodes for the Generation of White Light,” IEEE PHOTOICSTECHNOLOGY LETTERS, VOL. 18, NO. 24, Dec. 15, 2006, U.S. Pat. No.7,279,717, U.S. Pat. No. 7,042,017, U.S. Pat. No. 6,163,038, U.S. Pat.No. 7,361,937, U.S. Pat. No. 7,294,865, U.S. Pat. No. 7,279,716, andU.S. Patent Publication No. 2006/0,043,385, wherein U.S. Pat. No.7,279,716 teaches using red phosphor to generate white light.

Moreover, several other methods are developed, and those includes amethod, disclosed in U.S. Pat. No. 7,217,959, using a blue lightemitting layer composed of quantum dots formed on an active layeremitting blue light; a method, disclosed in U.S. Pat. No. 7,271,417, ofepitaxially forming a porous light-emitting layer, which can emit lightwith a plurality of wavelengths; and a method, disclosed in U.S. PatentPublication No. 2002/0,041,148, of epitaxially forming III-Vsemiconductor layer and II-V semiconductor layer to stack together, andemitting different wavelengths from them to mix a white light.

In all above exemplary prior arts, light emitting material emitting asecond wavelength light is disposed between an n-type conductive layerand a p-type conductive layer; however, such a configuration may easilychange the profile of a p-n junction, further affecting the lightemission or electrical characteristics of the light emitting diode. Inaddition, some prior arts still need phosphor; however, red phosphor haslow light conversion efficiency. Moreover, some prior arts needlithography and etching processes between two epitaxial growthprocesses, and the process steps are complex and may result in lowyield.

SUMMARY OF THE INVENTION

In view of the above description in Description of the Related Art andto meet industrial requirements, the invention provides a polychromaticlight emitting diode device, on which at least a wavelength conversionlayer is disposed, wherein the wavelength conversion layer is asemiconductor layer.

One objective of the present invention provides a light emitting diodedevice, which can be adapted to fit in any range on the CIE chromaticitydiagram.

Another objective of the present invention provides a white light sourcehaving good color rendering index (Ra).

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described according to the appended drawings inwhich:

FIG. 1 is a structure showing a light emitting diode device with awavelength conversion layer according to one embodiment of the presentinvention;

FIG. 2 is a rough surface formed on a wavelength conversion layeraccording to one embodiment of the present invention;

FIG. 3A is a transparent conductive layer formed during chip dicingprocess according to one embodiment of the present invention;

FIG. 3B is a depressed region etched out during chip dicing processaccording to one embodiment of the present invention;

FIG. 3C shows a p-electrode and an n-electrode formed during chip dicingprocess according to one embodiment of the present invention;

FIG. 4 shows n-electrode formed on the bottom of an epitaxial substrate,which is conductive, according to one embodiment of the presentinvention;

FIG. 5A shows a metal substrate formed during the removal of anepitaxial substrate according to one embodiment of the presentinvention;

FIG. 5B shows the removal of an epitaxial substrate and a buffer layerin a removal process of epitaxial substrate according to one embodimentof the present invention;

FIG. 5C shows an n-electrode and a p-electrode formed during the removalof an epitaxial substrate process according to one embodiment of thepresent invention;

FIG. 6 shows a structure for flip-chip packaging according to oneembodiment of the present invention;

FIG. 7 is a spectrum diagram showing a mixture of light from anultraviolet light layer and light from three wavelength transformationlayers according to one embodiment of the present invention;

FIG. 8 is a spectrum diagram showing a mixture of light from a bluelight layer and light from two wavelength transformation layersaccording to one embodiment of the present invention; and

FIG. 9 is a spectrum diagram showing a mixture of light from a bluelight layer and light from one wavelength conversion layer according toone embodiment of the present invention.

DETAILED DESCRIPTION

One aspect of the present invention suggests a light emitting device andfabrication method thereof. In order to thoroughly understand thepresent invention, detailed descriptions of method steps and componentsare provided below. Clearly, the implementations of the presentinvention are not limited to the specific details that are familiar topersons in the art related to a light emitting device and fabricationmethod thereof. On the other hand, components or method steps, which arewell known, are not described in detail. A preferred embodiment of thepresent invention will be described in detail as follows. However,except the preferred detailed description, other embodiments can bebroadly employed, and the scope of the present invention is not limitedby any of the embodiments, but should be defined in accordance with thefollowing claims and their equivalent.

The present invention utilizes at least one wavelength conversion layerformed on a surface of a light emitting device for the transformation ofa portion of light emitted from the light emitting device into light ofa different wavelength, which is mixed with the untransformed light toemit light having preferred CIE coordinates.

The present invention provides a polychromatic light emitting diodedevice comprising a substrate, a multiple semiconductor layer formed onthe substrate, and a first wavelength conversion layer formed on themultiple semiconductor layer. The multiple semiconductor layer comprisesan n-type semiconductor layer, a p-type semiconductor layer and anactive layer disposed between the n-type semiconductor layer and thep-type semiconductor layer, wherein the active layer emits a firstwavelength. The first wavelength conversion layer absorbs a portion ofthe first wavelength emitted from the active layer and emits a secondwavelength, wherein the second wavelength is longer than the firstwavelength.

The present invention provides a method for manufacturing apolychromatic light emitting diode device. The method first provides anepitaxial substrate. Next, a multiple semiconductor layer is formed onthe epitaxial substrate. Finally, a first wavelength conversion layer isformed on the multiple semiconductor layer. An n-type semiconductorlayer, a p-type semiconductor layer and an active layer disposed betweenthe n-type semiconductor layer and the p-type semiconductor layer, andthe active layer emits a first wavelength. The first wavelengthconversion layer absorbs a portion of the light of a first wavelengthemitted from the active layer and emits a second wavelength, wherein thesecond wavelength is longer than the first wavelength.

The material of the first wavelength conversion layer is a Group III-Vsemiconductor material or a Group II-VI semiconductor material. TheGroup III-V semiconductor material is Group III nitride, Group IIIphosphide or Group III arsenide. Moreover, the surface of the firstwavelength conversion layer can be a rough surface.

The present invention simultaneously comprises a second wavelengthconversion layer formed on the first wavelength transformation layer,wherein the second wavelength conversion layer absorbs the firstwavelength and the second wavelength from the first wavelengthconversion layer to emit a third wavelength, and the third wavelength islonger than the second wavelength. The material of the second wavelengthconversion layer is Group III nitride, Group III phosphide or Group IIIarsenide.

The Group II-VI semiconductor material is Group II oxide, Group IIsulfide or Group II selenide.

The epitaxial substrate is of sapphire (Al.sub.2O.sub.3), siliconcarbide (SiC), lithium aluminate (AlLiO.sub.2), lithium gallate(LiGaO.sub.2), silicon (Si), gallium nitride (GaN), zinc oxide (ZnO),aluminum zinc oxide (AlZnO), gallium arsenide (GaAs), gallium phosphide(GaP), gallium antimonide (GaSb), indium phosphide (InP), indiumarsenide (InAs), zinc selenide (ZnSe) or metal. The present inventionfurther comprises a buffer layer between the epitaxial substrate and themultiple semiconductor layer. The present invention further comprises ap-type electron blocking layer disposed between the active layer and thep-type semiconductor layer. In addition, the present invention furthercomprises a transparent conductive layer, which is formed on the firstwavelength conversion layer or the second wavelength transformationlayer, and is in ohmic contact with the first wavelength conversionlayer or the second wavelength transformation layer.

The epitaxial substrate can be of sapphire (Al.sub.2O.sub.3), siliconcarbide (SiC), lithium aluminate (AlLiO.sub.2), lithium gallate(LiGaO.sub.2), silicon (Si), gallium nitride (GaN), zinc oxide (ZnO),aluminum zinc oxide (AlZnO), gallium arsenide (GaAs), gallium phosphide(GaP), gallium antimonide (GaSb), indium phosphide (InP), indiumarsenide (InAs), or zinc selenide (ZnSe). The present inventioncomprises a buffer layer formed between the epitaxial substrate and themultiple semiconductor layer. The present invention further comprises ap-type electron blocking layer disposed between the active layer and thep-type semiconductor layer. In addition, the present invention moreovercomprises a transparent conductive layer, which is formed on the firstwavelength conversion layer and is in ohmic contact with the firstwavelength transformation layer.

The present invention additionally comprises an ohmic contact layerformed on the first wavelength transformation layer, wherein the ohmiccontact layer is in ohmic contact with the first wavelengthtransformation layer. The present invention further comprises a metalsubstrate formed on the ohmic contact layer. The present invention, aswell as, comprises a step of removing the epitaxial substrate.

To better understand the above-described objectives, characteristics andadvantages of the present invention, embodiments, with reference to thedrawings, are provided for detailed explanations.

Referring to FIG. 1, an epitaxial substrate 10 is first provided,wherein the following types of substrates can be used as the epitaxialsubstrate 10: a sapphire substrate, a silicon carbide substrate, alithium aluminate substrate, a lithium gallate substrate, a siliconsubstrate, a gallium nitride substrate, a zinc oxide substrate, analuminum zinc oxide substrate, a gallium arsenide substrate, a galliumphosphide substrate, a gallium antimonide substrate, an indium phosphidesubstrate, an indium arsenide substrate, or a zinc selenide substrate.The selection of an epitiaxial substrate depends on the material of anepitiaxially formed layer. For example, Group II-V semiconductor may beformed on a zinc selenide substrate or a zinc oxide substrate; Group IIIarsenide or Group III phosphide usually is formed on a gallium arsenidesubstrate, a gallium phosphide substrate, an indium phosphide substrate,or an indium arsenide substrate; and Group III nitride is commerciallyformed on a sapphire substrate or a silicon carbide substrate, whileGroup III nitride is experimentally formed on a lithium aluminatesubstrate, a lithium gallate substrate, a silicon substrate, or analuminum zinc oxide substrate. Furthermore, lattice structure andlattice constant are important basis to choose a substrate type. If thedifference of lattice constants is too large, a buffer layer is requiredto obtain good quality of an epitaxial layer. In the present invention,the epitaxial material is Group III nitride, especially gallium nitride,and is used with a sapphire substrate or a silicon carbide substrate.However, persons skilled in the art can understand the epitaxialmaterial is not limited to Group III nitride, or even gallium nitride.Any Group III-V semiconductor or Group II-VI semiconductor can apply inthe present invention.

A method of improving the quality of an epitaxial layer is initially toform a pattern on an epitaxial substrate 10 so that defects would notgrow following the growth direction of an epitaxial layer and finally toan active layer. The design of patterns depends on eptiaxial conditionsand quality. Relevant information can be found in TW Patent ApplicationNo. 096150701.

Due to the use of a sapphire substrate or a silicon carbide substrate, abuffer layer 12 is formed before epitaxial deposition of Group IIInitride. That is because the lattice mismatch between a sapphiresubstrate and gallium nitride is up to 14%. Similarly, the latticemismatch between a silicon carbide and gallium nitride is about 3.5%.Generally, the material of the buffer layer 12 can be gallium nitride,aluminum gallium nitride, aluminum nitride or InGaN/InGaN super latticestructure. The method for forming InGaN/InGaN super lattice structure isdisclosed in TW Patent Application No. 096104378. The buffer layer 12 isformed in an expitaxy equipment such as a metal organic chemical vapordeposition equipment or a molecular beam epitaxy equipment. Thetemperature of formation of the buffer layer 12 is lower than that offormation of the following expitaxial layer. For example, the epitaxialtemperature of InGaAlN is between about 800 and 1400 degrees Celsius,while the epitaxial temperature of the buffer layer 12 is between about250 and 700 degrees Celsius. If a metal organic chemical vapordeposition equipment is used, the precursor for nitrogen can be ammoniaor nitrogen, the precursor for gallium can be trimethylgallium ortriethylgallium, and the precursor for aluminum can be thetrimethylaluminum or triethylaluminum. The reactor can be at atmosphericpressure or low pressure.

Next, n-type gallium nitride layer or aluminum gallium nitride layer isformed for providing a light emitting diode an n-type cladding layer 14.The n-type gallium nitride layer or the n-type aluminum gallium nitridelayer is formed in a metal organic chemical vapor deposition equipmentor a molecular beam epitaxy equipment. During formation of the nitridelayer, a Group IV element is simultaneously doped. In the presentembodiment, the element is silicon, and the precursor for silicon usedin a metal organic chemical vapor deposition equipment can be silane ordisilane. Between the n-type cladding layer 14 and the buffer layer 12,an undoped gallium nitride layer (not shown) and an n-type contact layer(not shown) can sequentially formed, and these two layers are optional.The undoped gallium nitride layer is for improving the quality of then-type cladding layer 14, and the n-type contact layer, wherein then-type contact layer is a heavily doped gallium nitride layer or aheavily doped aluminum gallium nitride layer, is for providing betterelectrical conductivity between n-type electrodes.

Then, an active layer 16 is formed on the n-type cladding layer 14,wherein the active layer 16 is the light emitting layer of a lightemitting diode device, being able to have a heterogeneous structure, adouble heterogeneous structure, single quantum well structure ormultiple quantum well structure. The multiple quantum well structure ispresently adopted, including a multiple quantum well layer and a barrierlayer. The quantum well layer can be of indium gallium nitride, and thebarrier layer can be of a ternary compound such as aluminum galliumnitride. In addition, a quaternary compound such asAl.sub.xIn.sub.yGa.sub.1-x-yN can be used as the quantum well layer andthe barrier layer, wherein changing the ratios of aluminum and galliumcan separately obtain a barrier layer having high band gap energy and aquantum well layer having low band gap energy. The formation of theactive layer 16 is similar to the above-mentioned n-type cladding layer14, wherein the precursor for indium can be trimethylindium ortriethylindium. The active layer 16 can be doped with an n-type dopantor a p-type dopant, can be doped with n-type and p-type dopants, or isnot doped. Moreover, the quantum well layer can be doped, but thebarrier layer is not; the quantum well layer is not doped, but thebarrier layer is doped; or both quantum well layer and barrier layer arenot doped. Furthermore, a portion of the quantum well can be of deltadoping.

Next, a p-type electron blocking layer 18 is formed on the active layer16, and this step is optional. The p-type electron blocking layer 18 mayinclude a first Group III-V semiconductor layer and a second Group III-Vsemiconductor layer, which have different energy band gaps and aredeposited on the active layer 16 in a periodically repeating manner toform a electron blocking layer with energy barrier higher than that ofthe active layer 16 for blocking electrons overflowing out of the activelayer 16. The detailed descriptions and the manufacturing method of thep-type electron blocking layer 18 can refer to TW Patent Application No.097128065.

Next, a p-type gallium nitride layer or aluminum gallium nitride layeris formed for providing the light emitting diode a p-type cladding layer20. The p-type gallium nitride or the p-type aluminum gallium nitridelayer is formed in a metal organic chemical vapor deposition equipmentor a molecular beam epitaxy equipment. During the formation of thenitride layer, a Group II element is simultaneously doped. In thepresent embodiment, the element is magnesium, and the precursor formagnesium used in a metal organic chemical vapor deposition equipmentcan be CP.sub.2Mg. On the nitride layer 20, a p-type contact layer (notshown), which is optional, can be formed. The p-type contact layer canbe a heavily-doped gallium nitride layer or a heavily-doped aluminumgallium nitride layer, which is for providing better electricalconductivity between p-type electrodes.

Then, a wavelength conversion layer 40 is formed on the p-type claddinglayer 20 or the p-type contact layer. The material of the wavelengthconversion layer 40 can be a Group III-V semiconductor material or aGroup II-VI semiconductor material such as AlInGaAs, GaAs, InAs, AlAs,InGaAs, AlGaAs, InAlAs, AlInGaP, GaP, InP, AlP, InGaP, AlGaP, InAlP,AlInGaN, GaN, InN, AlN, InGaN, AlGaN, InAlN, ZnSe, ZnMgBeSSe, ZnCdSe,ZnMgSe, ZnSSe, ZrAgSSe, ZnMgSSe, ZnCdSe/ZnMgSSe orZnMgBeSe/ZnCdSe/ZnMgBeSe. The wavelength conversion layer 40, which isof a Group III-V semiconductor material or a Group II-VI semiconductormaterial, can be formed using a metal organic chemical vapor depositionprocess, a molecular beam epitaxy process, or a wafer bonding process,wherein the wafer bonding process directly bonds a formed wavelengthconversion layer onto a p-type cladding layer or a p-type contact layer.In the present embodiment, the wavelength conversion layer can be dopedto be p-type so as to reduce the electrical resistance.

In the active layer of a light emitting diode, the combination ofelectrons and holes produces a first wavelength. A portion of the firstwavelength excites the wavelength conversion layer so that a secondwavelength emits. To adjust the energy levels of the active layer andthe wavelength conversion layer can make the light emitting diode fit inany range on the CIE chromaticity diagram or provide white light havinggood color rendering index (Ra).

In the present invention, the wavelength transformation structure can beone or more layers, and multiple wavelength transformation layers can bea combination of different materials. For example, in a two-layersituation, one wavelength conversion layer can be Group III-Vsemiconductor and another can be Group II-VI semiconductor, or bothlayers can be either Group III-V semiconductor or Group II-VIsemiconductor. Moreover, the surface of the wavelength conversion layercan be a rough surface.

In one embodiment of the present invention, the active layer isInGaN/AlGaN multiple quantum well layer, which emits ultraviolet or nearultraviolet light having a wavelength in a range of 365 to 420nanometers, as shown in FIG. 7. The wavelength transformation structurecan have three layers: a first wavelength transformation layer, which isof InGaN and emits blue light with a wavelength in a range of 400 to 480nanometers; a second wavelength transformation layer, which is of InGaNand emits green or yellow-green light with a wavelength in a range of480 to 570 nanometers; and a third wavelength transformation layer,which is of GaP, GaAs, or InN and can emit yellow or red light with awavelength in a range of 580 to 650 nanometers.

In another embodiment of the present invention, the active layer is anInGaN/AlGaN multiple quantum well layer that can emit blue light with awavelength in a range of 440 to 460 nanometers, as shown in FIG. 8. Thewavelength transformation structure can have two layers: a firstwavelength transformation layer, which is of InGaN and emits green oryellow-green light with a wavelength in a range of 480 to 570nanometers; and a second wavelength transformation layer, which is ofGaP, GaAs, or InN and can emit yellow or red light with a wavelength ina range of 580 to 650 nanometers.

In the other embodiment of the present invention, the active layer is anInGaN/AlGaN multiple quantum well layer that can emit blue light with awavelength in a range of 440 to 460 nanometers, as shown in FIG. 9. Thewavelength transformation structure can have a wavelength transformationlayer, which is of GaP, GaAs, or InN and can emit yellow or red lightwith a wavelength in a range of 520 to 650 nanometers. In the aboveembodiments, yellow or green phosphors can be added in the finalpackaging step so that a packaged light emitting diode can emit whitelight having good color rendering index.

Referring to FIG. 2, if the material of the wavelength conversion layer42 is insulative, the transparent conductive layer 60 should beelectrically connected to either the p-type cladding layer 20 or thep-type contact layer. The simplest method to accomplish the electricalconnection is that a portion of the wavelength conversion layer 42 isremoved using an etching process or a partially covered wavelengthconversion layer 42 is directly formed by the manipulation of epitaxialprocess conditions. The etching process can be a dry etching process ora wet etching process.

The following steps are related to a die-dicing process for a lightemitting diode. As shown in FIG. 3A, a transparent conductive layer 60is formed on the wavelength conversion layer 40, wherein the transparentconductive layer 60 can be in ohmic contact with the wavelengthconversion layer 40. The material of the transparent conductive layer 60can be a material, which can be in ohmic contact with Group III nitride,such as Ni/Au, ITO, IZO, IWO or IGO, etc. The transparent conductivelayer can be formed using physical vapor deposition process such as avapor deposition process or a sputter deposition process.

Next, when the epitaxial substrate is a sapphire substrate or anon-conductive substrate, an n-electrode and a p-electrode are formed onthe same surface such that a structure with electrodes positioned on thesame side of a substrate is formed, as shown in FIG. 3C. In this processstep, a portion of the transparent conductive layer 60, the wavelengthconversion layer 40, the p-type contact layer (if formed), the p-typecladding layer 20, the active layer 16, the n-type cladding layer 14,and the n-type contact layer (if formed) are removed to form a depressedregion 70, as shown in FIG. 3B. The removal of those layers can beachieved by a dry etching process or a wet etching process. As shown inFIG. 3C, a p-electrode 90 is formed on the transparent conductive layer60, and an n-electrode 80 is formed on the exposed n-type cladding layer14 or on the n-type contact layer (if formed). The p-electrode 90 andn-electrode 80 can be formed using a physical vapor deposition processsuch as a vapor deposition process or a sputter deposition process. Thep-electrode 90 and n-electrode 80 can be patterned usinglithography-etching processes or a lift-off process.

After electrodes are formed, the epitaxial substrate is thinned down bya grinding process. The step is optional, and it is for improving thebrightness of the light emitting diode.

When the epitaxial substrate 10 is a silicon carbide substrate or aconductive substrate, it is unnecessary to remove a portion of thetransparent conductive layer 60, the wavelength conversion layer 40, thep-type contact layer (if formed), the p-type cladding layer 20, theactive layer 16, the n-type cladding layer 14, and the n-type contactlayer to expose the n-type cladding layer 14 or the n-type contact layer(if formed). As shown in FIG. 4, n-electrode 82 can be directly formedon the bottom of the epitaxial substrate 10, and the p-electrode 92 canbe formed close to the central area of the transparent conductive layer60.

Moreover, when the epitaxial substrate 10 is a sapphire substrate, itcan be removed by the substrate lift-off technology as shown in FIG. 5.At this moment, a metal substrate 11 should be formed on the oppositesurface to provide a support when the substrate 10 is under lift-offstress, as shown in FIG. 5A. If the substrate lift-off technology isadopted, the ohmic contact layer 62 formed following the wavelengthconversion layer need not be transparent. The substrate lift-offtechnology can be a laser lift-off process; or the epitaxial substrate10 and the buffer layer 12 can be removed using a wet chemical etchingprocess ash shown in FIG. 5B. As shown in FIG. 5C, the wafer is thenflipped over to make the n-type cladding layer 14 face upward. Ap-electrode 94 is formed on the metal substrate 11, and an n-electrode84 is formed on the n-type cladding layer 14. A method using aconductive substrate or the substrate lift-off technology can obtain astructure with an n-electrode and a p-electrode formed on two oppositesurfaces of the substrate.

Thereafter, the entire wafer is diced to obtain a plurality of dies. Thewafer can be diced using a wafer saw or a laser to obtain individualchips or dies. The diced chips or dies are bonded to a die attach film,waiting for the next process.

Referring to FIG. 6, the present invention may use a flip chip packagemethod for chip packaging. Using the wafer dicing technology only canadopt the structure with electrodes on the same side of a substrate.During chip packaging, the n-electrode and the p-electrode of a chip ora die with electrodes on the same side thereof are directly bonded to apackage substrate 100.

The method of the present invention forms at least one wavelengthconversion layer on a surface of a light emitting to produce white lightor polychromatic light, wherein the wavelength conversion layer is madeof semiconductor, which can produce light with any desired wavelength.Moreover, the packaged light emitting diode of the present invention canproduce white light without adding any phosphor or can provide whitelight having good color rendering index (Ra).

In view of the means and effects of the present invention, the presentinvention has many advantages. First, the wavelength conversion layercan be completely formed in a reactor chamber without using lithographyprocess, reducing the risk of contamination. In addition, compared toprior art technologies, the location of p-n junction would not change soas to remain the original light emission efficiency. Moreover, thewavelength conversion layer is a semiconductor, and therefore, theenergy level thereof can be changed according to the requirement ofwavelength. Further, the surface of the wavelength conversion layer canbe a rough surface, which increases light emission efficiency.

The above-described embodiments of the present invention are intended tobe illustrative only. Numerous alternative embodiments may be devised bypersons skilled in the art without departing from the scope of thefollowing claims.

1. A method for manufacturing a polychromatic light emitting diodedevice, comprising steps of: providing an epitaxial substrate; forming amultiple semiconductor layer on said epitaxial substrate, wherein saidmultiple semiconductor layer comprises an n-type semiconductor layer, ap-type semiconductor layer and an active layer disposed between saidn-type semiconductor layer and said p-type semiconductor layer, and saidactive layer emits light of a first wavelength; forming a firstwavelength conversion layer on said multiple semiconductor layer, thefirst wavelength conversion layer having a plurality of indentations,wherein said first wavelength conversion layer is made of semiconductorand said first wavelength conversion layer absorbs a portion of saidlight of a first wavelength emitted from said active layer and emitslight of a second wavelength, wherein said second wavelength is longerthan said first wavelength; and forming a transparent conductive layeron said first wavelength conversion layer, wherein said transparentconductive layer is in direct contact with said multiple semiconductorlayer via said plurality of indentations of the first wavelengthconversion layer.
 2. The method of claim 1, wherein the material of saidfirst wavelength conversion layer is a Group III-IV semiconductormaterial or a Group II-IV semiconductor material, wherein said groupIII-V semiconductor material is Group III nitride, Group III phosphideor Group III arsenide semiconductor.
 3. The method of claim 2, furthercomprising a step of forming a second wavelength conversion layer onsaid first wavelength conversion layer, wherein said second wavelengthconversion layer absorbs said light of a first wavelength and said lightof a second wavelength from said first wavelength conversion layer andemits light of a third wavelength, and said third wavelength is longerthan said second wavelength.
 4. The method of claim 3, wherein thematerial of said second wavelength conversion layer is Group III nitridesemiconductor, a Group III phosphide semiconductor or a Group IIIarsenide semiconductor.
 5. The method of clam 1, further comprising astep of forming a buffer layer between said substrate and said multiplesemiconductor layer and a p-type electron blocking layer between saidactive layer and said p-type semiconductor layer.
 6. The method of claim1, further comprising a step of forming a metal substrate on saidtransparent conductive layer.
 7. The method of claim 6, furthercomprising a step of removing said epitaxial substrate.
 8. The method ofclaim 7, further comprising steps of: forming a second wavelengthconversion layer on said first wavelength conversion layer; and forminga third wavelength conversion layer on said second wavelength conversionlayer.
 9. The method of claim 8, wherein said active layer emitsultraviolet light; and said first wavelength conversion layer, saidsecond wavelength conversion layer, and said third wavelength conversionlayer separately emit blue light, green light and red light.
 10. Amethod for manufacturing a polychromatic light emitting diode device,comprising steps of: providing an epitaxial substrate; forming amultiple semiconductor layer on said epitaxial substrate, wherein saidmultiple semiconductor layer comprises an n-type semiconductor layer, ap-type semiconductor layer and an active layer disposed between saidn-type semiconductor layer and said p-type semiconductor layer, and saidactive layer emits light of a first wavelength; and forming a firstwavelength conversion layer on said multiple semiconductor layer,wherein said first wavelength conversion layer is made of semiconductorand said first wavelength conversion layer absorbs a portion of saidlight of a first wavelength emitted from said active layer and emitslight of a second wavelength, and wherein said second wavelength islonger than said first wavelength.
 11. The method of claim 10, furthercomprising a step of forming a transparent conductive layer on saidfirst wavelength conversion layer, said transparent conductive layerbeing in electrical connection with said multiple semiconductor layer.12. The method of claim 11, wherein said transparent conductive layer isin direct contact with said multiple semiconductor layer.
 13. The methodof claim 12, wherein said first wavelength conversion layer has aplurality of indentations and said transparent conductive layer is indirect contact with said multiple semiconductor layer via said pluralityof indentations of the first wavelength conversion layer.
 14. The methodof claim 10, wherein the material of said first wavelength conversionlayer is a Group III-IV semiconductor material or a Group II-IVsemiconductor material, wherein said group III-V semiconductor materialis Group III nitride, Group III phosphide or Group III arsenidesemiconductor.